Influenza vaccination has a potential protective effect against adverse events within 120 days of a positive severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) diagnosis, according to a study published online Aug. 3 in PLOS ONE.

Susan M. Taghioff, from the University of Miami Miller School of Medicine, and colleagues used a continuously updated Electronic Medical Record network to assess the possible benefits of influenza vaccination in mitigating critical adverse outcomes in patients who were SARS-CoV-2-positive. The deidentified records of 73,346,583 patients were screened retrospectively. Two cohorts were created with 37,377 patients who had or had not received influenza vaccination six months to two weeks prior to a SARS-CoV-2-positive diagnosis. Adverse outcomes within 30, 60, 90, and 120 days of a positive SARS-CoV-2 diagnosis were examined.

The researchers found that across all time points, SARS-CoV-2-positive patients who received the influenza vaccine experienced significant reductions in sepsis and stroke. At 30, 90, and 120 days, SARS-CoV-2-positive patients who had received the influenza vaccine had significantly lower intensive care unit admissions; the finding approached significance at 60 days. Fewer deep vein thromboses were experienced at 60 to 120 days after a positive SARS-CoV-2 diagnosis among patients who had received the influenza vaccine. There were also significantly fewer emergency department visits at 90 to 120 days after a SARS-CoV-2-positive diagnosis.

"Future prospective controlled studies to validate these findings and determine if an increased emphasis on influenza vaccination will improve adverse outcomes in SARS-CoV-2-positive patients will be beneficial," the authors write.

One author disclosed financial ties to the medical device industry.